Method for the preparation of CdS or CdSe powder for electrophotography

ABSTRACT

This invention relates to treating CdS or CdSe powder by adding silver or copper as an activator and then firing in an atmosphere of sulfur vapor to produce CdS or CdSe powder suitable for use in an electrophotographic photoconductive member. The CdS or CdSe powder thus produced is mixed with a bonding resin to form a photosensitive layer and an electrophotographic photoconductive plate is made therefrom.

United States Patent Hanada et a1.

METHOD FOR THE PREPARATION OF CDS OR CDSE POWDER FOR ELECTROPHOTOGRAPHY Inventors: Hiroshi Hanada, Yokohama; Nobuo Kitajima, Tokyo, both of Japan Assignee: Canon Camera Kabushiki Kaisha,

Tokyo, Japan Filed: July 30, 1973 Appl. No.: 383,610

Related U.S. Application Data Continuation of Ser. No 164,464, July 20, 1971,

abandoned, which is a division of Ser. No. 734,637, June 5, 1968, abandoned,

U.S. Cl. 96/].5; 252/501; 423/99;

423/509 lnt. Cl. G03G 5/04 Field of Search 96/].5, 1.6; 252/501;

References Cited UNITED STATES PATENTS 12/1958 Briggs 252/501 451 July 22, 1975 2,876,202 3/1959 Busanovich 252/501 3,519,480 7/1970 Trautweiler.... 117/201 3,595,646 7/1971 Kinoshita 106/301 3,598,760 8/1971 Nakamura 252/501 Primary E.raminer-Norman G. Torchin Assistant Examiner-Judson R. Hightower Armrney, Agent. or Firm-Fitzpatrick. Cella. Harper & Scinto 2 Claims, 1 Drawing Figure PATENTED JUL 22 m5 :3 a 85; 943

METHOD FOR THE PREPARATION OF CDS OR CDSE POWDER FOR ELECTROPHOTOGRAPHY This is a continuation, of application Ser. No. 164,464, filed July 20, l97l, now abandoned which was a divisional of application Ser. No. 734,637 filed June 5, I968, now abandoned.

This invention relates to a method of the preparation of CdS or CdSe powder for electrophotography and a method of making an electrophotographic photosensitive plate by using the powder.

It is well known that pure CdS or CdSe powder is activated with silver or copper to form a photoconductive material. However, the object of the prior art above is to produce a photoconductive material which is predominantly used in a usual photoconductive apparatus, but the photoconductive material thus obtained is not suitable for electrophotography.

Heretofore, a photoconductive material has been directly considered to be a suitable electrophotographic material. However, with respect to an electrophotographic system utilizing a persistent internal polarization, the conventional relation as above that a photoconductive material is always a suitable electrophotographic material is not established. Therefore, it is not appropriate to use a conventional photoconductive member as an electrophotographic material.

The object of this invention is to provide a method of preparing CdS or CdSe powder suitable for the preparation of an electrophotographic photoconductive plate used in a method of a persistent internal polarization type.

Another object of this invention is to provide a method of making an electrophotographic photoconductive plate by using the CdS or CdSe powder obtained by the invention.

In the prior art, a photoconductive material was prepared by the following three steps, i.e., (i) adding silver or copper as an activating agent (the first firing step), (ii) adding a halogen as a co-activating agent (the second firing step), and (iii) firing in an atomsphere of sulfur vapor to decrease the dark current (the third firing step), or by the above mentioned steps (i) and (ii) excluding the step (iii) when zinc chloride is used as a flux.

According to the method of this invention, the step (ii) (introducing a halogen) as mentioned above in the prior art is omitted and only the two steps, that is, the first firing step for adding silver or copper and the third firing step for treating with sulfur vapor, are employed to produce CdS or CdSe powder suitable for an electrophotographic material.

According to the second method of this invention, the CdS or CdSe powder prepared by the first method of this invention as mentioned above is mixed with a binder resin and the resulting mixture is made into a layer of 50 lOOu thickness between a support and an insulating film to form an electrophotographic photosensitive plate. The attached drawing illustrates an embodiment of the photosensitive plate obtained by the method of this invention.

With reference to the drawing, the photosensitive plate comprises a support I, a photosensitive layer 2 which is formed by bonding the CdS or CdSe powder prepared by the first method of this invention with a resinous material such as, for example, a synthetic resin, and an insulating layer 3.

The final properties of CdS or CdSe powder obtained by the method of this invention are free from dispersion and the powder size is very small. Thus, the sharpness of the image is markedly improved and further when the powder thus obtained is used for a photoconductive plate, the resulting photoconductive plate gives an image of high contrast. Furthermore, the process for the preparation is simple as compared with the prior art since the second step is omitted.

The following examples are set forth for purposes of illustration only and are not to be construed as limitations on the present invention except as set forth in the appended claims.

EXAMPLE 1 Pure cadmium sulfide I00 g., cadmium chloride 10 g., ammonium chloride 1 g., cupric chloride 0.03 g., and deionized water 250 cc. are thoroughly mixed, dried, placed in a quartz test tube, fired in an atmosphere of nitrogen for 30 minutes at 600C, washed with water, dried, screened by a 325 mesh screen, placed together with 0.2 g. of sulfur powder in a quartz test tube, and fired in an atmosphere of nitrogen at 500C for 10 minutes and then under vacuum for further 10 minutes.

EXAMPLE 2 Cadmium sulfide powder (high purity) g., zinc oxide 6 g., ammonium chloride 1 g., 12N hydrochloric acid 12.4 cc., cupric chloride 0.03 g., and water 20 cc. are sufficiently mixed to form a paste and dried. The dried blocks are crushed to particles of a size of a bean, placed in a quartz test tube, fired in an atmosphere of chloride and stagnant air for 20 minutes at 600C, washed with water, dried and thereafter subjected to the similar treatments subsequent to the washing with water and drying step as in Example 1.

EXAMPLE 3 By using cadmium selenide powder in place of cadmium sulfide, the procedures in Example l or Example 2 are repeated.

EXAMPLE 4 Epoxy resin Epikote 815 (Trade name) containing about 12% by weight of an amine series hardener K-6l B is added as a bonding agent to CdS powder obtained in Example 1 or Example 2 at an amount of about 15% by weight on the basis of the CdS powder, sufficiently mixed, and the resulting mixture is transferred onto an aluminium foil and then rapidly spread and leveled off to a thickness of about 8011.. The leveling is carried out by using a frame of thin metal plate as a spacer, covering the above-mentioned mixture with a Mylar insulating film of about 25 u in thickness, and leveling off the mixture through the Mylar film with an edge of a metal bar having a wedge-like cross section to form a thin layer.

EXAMPLE 5 The mixture as used in Example 4 above is put on a Mylar film placed on a flat plate and directly leveled off to form a photosensitive layer. Then, the resulting whole matter is turned upside down and placed on an appropriate support.

EXAMPLE 6 in Example 4 above, an insulating film such as Mylar is used in place of the metal foil.

The photosensitive plate as mentioned above is positively charged by corona discharging in a light or dark place. exposed to an image irradiation at an intensity of 10 lux. sec., and similarly nagatively charged by corona discharging. Finally, the whole photosensitive plate is exposed to light. The effects of these steps from a physical point of view is as follows. The positive surface potential formed by the initial charging induces a polarization in the photosensitive plate. This polarization persists at a dark portion of the image when the image irradiation is effected simultaneously with the negative charging. Therefore, the charge at the light portion is changed to negative charge while the negative charging does not proceed at a dark portion due to repulsion of the polarity and a slightly neutralized state appears. Then, when the persistent internal polarization disappears by the final whole irradiation, electrostatic latent images of negative potential and nearly neutral poten tial are produced on the photosensitive plate.

By using the photosensitive plate having the structure as mentioned above, the electrostatic contrast of the electrostatic latent image formed by using a conventional photoconductive member is compared with that formed by using the material obtained by this invention. The result is shown in Table l below.

Table 1 surface potensurface potenelectrotial at a tial at a static light portion dark portion contrast Photoconductive plate prepared 900 I00 1000 by a conventional method Photnconductive plate prepared i200 I50 I350 by this invention (unit: volt) The above data clearly indicates that the photosensitive plate made of the material prepared by the method of this invention comprising two steps including a sulfur treating step excluding the second firing step in the conventional process which has been considered as an indispensable treatment for improving the property of photoconductive member shows an excellent performance.

What is claimed is:

l. A process for preparing CdS or CdSe powder useful as an electrophotographic material in an electrophotographic process which method consists of: i ac tivating the Cds or CdSe powder by adding thereto silver or copper as an activator as a silver or copper compound and firing the resulting mixture in the presence of hydrochloric acid and at least one member selected from the group consisting of cadmium chloride and zinc oxide; (2) washing the powder produced by step (i) with water; (3) drying the water-washed powder; and (4) firing the dried powder in an atmosphere of sulfur vapor.

2. The process of claim 1 wherein the first firing is carried out at a temperature of 600C. for 20-30 minutes and the second firing is carried out at a temperature of 500C. for l0 minutes in an atmosphere of sulfur vapor and thereafter under vacuum for 10 minutes.

UNHl-JD s'm'nas IA'll-LNT (mum-1 CERTIFICATE 01* CORRECTION Patent No. 3,895 Dated July 2 I 1975 Invent0r(s) HIROSHI HANADA, ET AL It is certified that error appears in the above-identified patent. and that said Letters Pa tent are hereby corrected as shown below:

On the cover page, between items [2l and [60] on the left hand column, insert:

[30] FOREIGN APPLICATION PRIORITY DATA June 8, 1967' -Japan -36627/l967 ,bigncd and Scaled this sixteenth Day Of September 1975 [SEAL] Arrest:

C. MARSHALL DANN RUTH C. MASON (ummissimwr nj'ParenIs and Trademarks Arresting Officer UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 3,895,943

DATED July 22 1975 INVENTOHS) HIROSHI HANADA, ET AL.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 1, lines 6-9, the language "in the presence of hydro chloric acid and at least one member selected from the group consisting of cadmium chloride and zinc oxide" should instead read as follows:

in the presence of at least one member selected from the group consisting of (a) cadmium chloride and (b) zinc oxide together with hydrochloric acid.

Signcd and Scaled this A nest:

LUTRELLE F. PARKER RUTH C. MASON Arresting Oflicer Acting Commissioner of Parents and Trademarks 

1. A PROCESS FOR PREPARING CDS OR CDSE POWDER USED AS AN ELECTROGRAPHIC MATERIAL IN AN ELECTROGRAPHIC PROCESS WHICH METHOD CONSISTS OF: (1) ACTIVATING THE CDS OR CDSE POWDER BY ADDING THERETO SILVER OR COPPER AS AN ACTIVATOR AS A SILVER OR COPPER COMPOUND AND FIRING THE RESULTING MIXTURE IN THE PRESENCE OF HYDROCHLORIC ACID AND AT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OF CADMIUM CHLORIDE AND ZINC OXIDE, (2) WASHING THE POWDER PRODUCED BY STEP (1) WITH WATER, (3) DRYING THE WATER-WASHED POWDER, AND (4) FIRING THE DRIED POWDER IN AN ATMOSPHERE OR SULFUR VAPOR.
 2. The process of claim 1 wherein the first firing is carried out at a temperature of 600*C. for 20-30 minutes and the second firing is carried out at a temperature of 500*C. for 10 minutes in an atmosphere of sulfur vapor and thereafter under vacuum for 10 minutes. 